Abstract
Dense graded asphalt concrete is widely used in roads as support structure for vehicle loads, however, is also used for hydraulic purposes in canal linings as well as faces and cores of dams. In the design stage of these constructions it is necessary to have the permeability data of the materials that will be used and, although in some cases it is sufficient to know this parameter in only one direction, in others it is necessary to have it in two directions. This research presents test results of axial permeability in constant head permeameter and the design a of radial permeability test device in asphalt concrete made for hydraulic purposes. As a result it was determined that the compaction process of asphalt concrete, applied in one direction, causes the material to have anisotropic behavior from the hydraulic point of view, resulting in anisotropy ratios 7.1 to 10.4, for the studied asphalt mixture.
Highlights
Asphalt concrete has been widely used as building material, mainly in road construction and, to a lesser extent, in impermeable barriers
This study presents the laboratory results in which the combination of permeability tests with axial flow and radial flow was used to determine the degree of hydraulic anisotropy of dense graded asphalt concrete
It was determined that asphalt concrete is a material that presents a hydraulic anisotropy (A) with values between 7,1 and 10,4, for the mixture used in this study
Summary
Asphalt concrete has been widely used as building material, mainly in road construction and, to a lesser extent, in impermeable barriers. Commission on Large Dams, which presents in its bulletin 84 (ICOLD, 1992) a detailed report on this type of dams built up to its publication date In these structures, it is of supreme importance to know the hydraulic conductivity of the materials from which it will be formed, and, for this purpose, tests are carried out to determine its permeability coefficient (k). When the water passes through a porous medium where the flow is laminar, the well-known Darcy’s law given by Equation (2) is fulfilled, where U is the discharge velocity, k is the permeability coefficient and i is the hydraulic gradient. In tests made on asphalt concrete by Waters (1990), it can be noted that when the discharge velocity is greater, the coefficient n, tends to 0,5 This value approaches notably 1,0 when the discharge velocity decreases. Gsb= Bulk specific gravity Gsss= Saturated surface dry specific gravity Gsa= Apparent specific gravity Source: Authors
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